Portable instrument and method for measuring the air permeability of plant leaves

Abstract

To indicate stomatal aperture in plant leaves, this instrument measures the permeability to air flow across the leaf. Air entrance and exit chambers are temporarily and non-destructively sealed on opposite sides of the leaf. The entrance chamber is pressurized while the exit chamber remains sealed as an initial test for any leakage. The exit chamber is then opened to the atmosphere and the time required for a specific volume of air to move across the leaf is measured.

What is claimed is: 
     
       1. A instrument held in one hand for measuring the air permeability of a plant leaf comprising: air inlet means which is placed over at least a part of a leaf surface and air outlet means which is placed over at least a part of the opposite surface;   means for holding the air inlet and air outlet means in place on the surfaces of the leaf while measurements of the air permeability between the air inlet and the air outlet are taken;   pump means for introducing pressurized air in order to pressurize the air inlet;   means for measuring the pressure of air at the air inlet;   means for releasing the pressurized air from the air outlet;   means for timing any change in air inlet pressure while the air outlet means remains closed; and   means for timing any change in air inlet pressure after the air outlet means is opened.   
     
     
       2. An instrument held in one hand for measuring the air permeability of a leaf comprising: entrance and exit chambers surrounded by flexible but firm gaskets;   a clamp affixed to said chambers, which can be opened with the same hand which holds the instrument and with that some hand closed on opposite sides of the leaf;   a spring attached to said clamp which provides a steady, but adjustable, clamping pressure throughout a measurement;   a finger pump, which pressurizes the entrance chamber, which is operated by the same hand which holds the instrument;   a dial pressure gauge which measures the entrance chamber pressure;   an exit chamber release valve which is operated by the same hand which holds the instrument; and   a timing device which in routine use starts when the exit chamber release valve is pressed and stops when the valve is released.   
     
     
       3. An instrument as in claim 2 wherein the pressure gauge is electronic.